ni52: clean up initialization of priv

* initialize spinlock once
* check586() used to be done before we'd allocated ->priv; these days
  it's there from the very beginning, so we don't have to play with
  private copy.  Consequently, we don't need to mess with reinitializing
  ->base, etc. afterwards.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>